This 1 USD “product” – which has unit price being USD 1.00 $ – is a solution to help you pay a custom amount. Because “amount to pay” = quantity x unit price 1$, so to pay a specific amount, you just simply type the quantity, then update cart.
For example, if you want to pay USD450 to us. How to do? You can add this “1 USD product” to your cart. Change the quantity to 450. Then, update cart. So, you can pay USD450